FIG. 1 is a structural diagram showing one example of the prior art tape loading mechanism. In this figure, reference numeral 1 represents a chassis, reference numeral 2 represents a rotary head drum, and reference numeral 3 represents a tape cassette accommodated in the chassis 1 having a supply reel 24 from which the length of magnetic tape 4 is drawn so as to be turned around the rotary head drum and as to be wound around a tape-up reel 23. Reference numerals 25 and 26 represent respective guide rods disposed inside the tape cassette 3. Reference numerals 5 and 6 represent respective guide grooves formed one on each side in the chassis 1, reference numerals 7 and 8 represent respective guide post member slidably supported in the associated guide grooves 5 and 6, reference numerals 9 and 10 represent respective guide stopper rigidly mounted on the chassis 1 for receiving the associated guide post members 7 and 8 during a loading condition, and reference numeral 11 represents a capstan drive motor for driving a capstan shaft 12. Reference numeral 13 represents a pinch roller support arm pivotally mounted on the chassis 1 through a support pin 14 rigidly mounted upright on the chassis 1, said pinch roller support arm having a free end carrying a pinch roller 15 rotatably mounted thereon.
The pinch roller support arm 13 and a driving means therefor are illustrated in FIG. 2. Reference numeral 16 represents a cam plate pivotally mounted on a support shaft of the pinch roller 15 and having a generally intermediate portion thereof provided with a tape guide 17. This cam plate 16 is normally biased in a counterclockwise direction, as viewed in FIG. 2, by a spring member (not shown) and is, so far illustrated, so biased that a free end of the cam plate 16 is engaged to an abutment member 22. When the pinch roller support arm 13 is pivoted in a counterclockwise direction, the cam plate 16 is so pivoted with its free end disengaged from the abutment member 22 and subsequently engaged to a stopper 13a provided on the pinch roller support arm 13. Reference numeral 18 represents a link plate supported for sliding movement in one of the opposite directions, shown by the arrows A and B, while guide by support pins 26 rigidly mounted on the chassis 1 so as to protrude upright from the chassis 1, which link plate 18 can be moved by a loading drive motor through a motion transmitting means (both not shown). Reference numeral 19 represents a slide plate supported slidably on the link plate 18, which plate 19 is normally urged in a direction shown by the arrow A by the action of a tension spring 20 disposed between it and the link plate 18 and is formed with a slot 19a. An engagement pin 21 rigidly secured to a rear end of the pinch roller support arm 13 is engaged in the slot 19a and is operable to rotate the pinch roller support arm 13 when the slide plate 18 is moved.
The operation of the prior art device of the above described construction is as follows. The tape cassette 3 having the length of magnetic tape 4 accommodated therein is placed on the chassis 1. While in this unloading condition, the loading drive motor is driven to move the guide post members 7 and 8 along the guide grooves 5 and 6, respectively, through the motion transmitting means (not shown) to establish a first loading condition.
On the other hand, during the unloading condition, the pinch roller support arm 13 is in a pivoted position shown by the chain line by the action of the link plate 18 held at a position biased in the direction shown by the arrow B in FIG. 2 and, therefore, the cam plate 16 is engaged to the stopper 13a. By the rotation of the loading drive motor for the loading, the link plate 18 is moved in the direction shown by the arrow A through the motion transmitting means (not shown). In this way, the pinch roller support arm 13 is pivoted in a clockwise direction to assume a position shown by the solid line and, therefore, the first loading condition is established wherein the length of magnetic tape 4 does not contact the pinch roller 16, but contact the tape guide 17.
During this first loading condition, the guide post members 7 and 8 are positioned as received by the respective guide stoppers 9 and 10 and the length of magnetic tape 4 is turned a predetermined angle around the rotary head drum 2, but pinch roller 15 is disengaged from both of the length of magnetic tape 4 and the capstan shaft 12, permitting the length of magnetic tape 4 to be transported by the rotary drive of the take-up reel 23. In other words, the length of magnetic tape 4 drawn out from the supply reel 24 is wound upon on the take-up reel 23 after having passed through the guide post member 8, then through the rotary head drum 2, and finally through the guide post member 7.
Also, when the loading drive motor is rotated, the link plate 18 is moved in a direction shown by the arrow A to establish a second loading condition shown in FIGS. 1 and 2. During the movement of the link plate 18, the cam plate 16 is engaged to the abutment member 22 to rotate in a clockwise direction and the pinch roller 15 is brought into engagement with the capstan shaft 12 through the length of magnetic tape 4 and is pressed thereagainst by the action of the tension spring 20. The tape guide 17 is rigidly mounted on the cam plate 16 and, therefore, during the second loading conditions, the position of the tape guide 17 is determined by pinch roller support arm 13 and the engagement between the cam plate 16 and the abutment member 22.
Thus, when the second loading condition is established at which the loading completes, the length of magnetic tape 4 is pressed against the capstan shaft 12 by the pinch roller 15 and can be transported by the drive of the capstan drive motor 11. In this way, the length of magnetic tape 4 is transported past the guide post member 7 and is guided along the tape guide 17 and the guide rod 25 via the capstan shaft 12, finally being wound up around the take-up reel 23.
In the above described prior art tape loading mechanism, the position of the tape guide 17 is determined by the engagement between the link plate 18 and the pinch roller support arm 13 during the first loading condition and tends to be affected by an error in position of the link plate 18 to such an extent that the accuracy of the positioning of the tape guide 17 may be insufficient.
Also, even during the second loading conditions, the position of the tape guide 17 is determined by the pinch roller support arm 13 and the engagement between the cam plate 16 and the abutment member 22 and, therefore, the accuracy of the positioning of the tape guide 17 tends to be insufficient. Because of this reason, the winding angle of the tape guide 17 is not fixed and, therefore, there has been a problem in that stable transport of the length of magnetic tape is difficult to achieve.
Moreover, there are many parts which are engaged with the tape guide 17 and the guide post members 7 and 8 and dimensional relationship among them can not be easily attained. By way of example, dimensional accuracy between the tape guide 17 and the guide post members 7 and 8 can not be easily attained during the unloading condition shown by the single-dotted line in FIG. 3 and, at the time the tape cassette 3 is mounted onto the chassis 1, the tape guide 17 and some other parts cannot be accommodated within an interior space 3a in the tape cassette 23, posing a problem in that they tend to contact the length of magnetic tape 4.